Method for Improving Strength and Dyeing of Wool Fibers

ABSTRACT

The disclosure provides a method for improving the strength and dyeing of wool fibers, and belongs to the technical field of modification of textile materials. By using the feature that protein fiber macromolecules contain a large number of active groups such as hydroxyl groups, amino groups and carboxyl groups, which easily react with polyphenolic pigments formed by a phenolic compound catalyzed by an enzyme to form covalent bonding, the disclosure realizes low temperature dyeing of wool fibers while improving the fiber strength. The disclosure has mild operating conditions easy to control, and in view of increasingly emphasis on environmental protection nowadays, the use of the biological enzyme for dyeing wool fibers is safe, environmentally friendly and efficient, and has a long-term development prospect.

TECHNICAL FIELD

The disclosure relates to a method for improving the strength and dyeing of wool fibers, and belongs to the modification technology of textile materials.

BACKGROUND

Protein fibers such as wool fibers have excellent hygroscopicity and warmth retention, are soft to wear, and are widely used in the textile industry. However, during the processing like scouring, spinning, weaving and dyeing, the wool fibers will be damaged and the mechanical properties will be deteriorated. It is worth noting that due to the hydrophobicity of a scale layer on the surface of wool, a high temperature process is often used for wool dyeing, which causes strength damage, seriously affects the subsequent processing of the fibers and the wearing performance of the fabric, consumes a lot of energy and is unfavorable to the environment. Therefore, it is of great significance to seek a mild and effective dyeing method for preventing and repairing wool fiber damage.

In the prior art, there are a few reports on the repair of strength damage to wool fibers, and in some reports they use chemical cross-linking agents, such as glyoxal, glutaraldehyde, dioctyl ester and carbodiimide. These cross-linking agents are cheap and can easily improve the tensile properties of fibers, but they pose a great threat to the environment and the health of users. At present, there is extensive research on transglutaminase (TG) in repairing strength damage of wool. TG has the ability to absorb primary amines and graft peptide chains (containing glutamine or lysine residues) into proteins, which can repair multiple damages such as chemical damage and biological damage to wool, but has a single purpose.

Protein fibers are dyed mainly with acid dyes and reactive dyes by physical or chemical combination with fibers. However, with the depletion of world energy and deterioration of environmental problems, development of synthetic dyes and the printing and dyeing industry is faced with many problems such as environmental pollution and high labor costs. Finding new eco-friendly dyes has become a new development direction.

SUMMARY Technical Problems Solved

The disclosure provides a method for biologically enzymatical dyeing and improving the strength of wool fibers, including: firstly, pretreating wool yarn by a physical or chemical method, and then dyeing the pretreated wool yarn in a laccase-phenolic compound reaction system. Protein fiber macromolecules contain a large number of active groups such as hydroxyl groups, amino groups and carboxyl groups, which could easily react with colored enzymatic phenolic polymerization products to form covalent bonding, thereby realizing low-temperature dyeing of wool fibers and endowing the fibers good dyeing performance and mechanical properties. The reaction conditions are mild, easy to control, green and environmentally friendly, and the method shows broad development prospects.

Laccase is a copper-containing oxidoreductase found in many plants, fungi and microorganisms. In textile processing, laccase is used for improving the whiteness of fabrics during bleaching, decolorization of colored wastewater, refining of fibers, and anti-felting of wool, but there is no report on improving the strength of wool fibers. The disclosure uses the laccase to catalyze the reaction of a substrate to produce a colored polymerization product, which reacts with a large number of active groups such as hydroxyl groups, amino groups and carboxyl groups in protein fiber macromolecules to form covalent bonds, so that in-situ dyeing is achieved and the strength of wool fibers is also improved.

Technical Solutions

The first objective of the disclosure is to provide a method for improving the strength and dyeing of wool fibers, and the method includes: adding a laccase and phenolic compound mixed system into a buffer solution, and wool fibers was dyed in a reaction system containing this laccase and phenolic compound system.

In an implementation of the disclosure, the phenolic compound is catechol, hydroquinone, gallic acid, vanillin, guaiacol and the like.

In an implementation of the disclosure, before enzyme-catalyzed reaction of the phenolic compound with wool, wool fibers need to undergo pretreatment by a chemical, enzymatic or physical method.

In an implementation of the disclosure, the pretreatment may be carried out by using sodium carbonate, and the formula and conditions of the treatment process are as follows: weighing wool fibers and sodium carbonate, dissolving the sodium carbonate in deionized water to prepare a sodium carbonate solution of 0.5-1 g/L, and at a bath ratio of 1:20 to 1:50, soaking and treating the wool fibers in the sodium carbonate solution at 30-80° C. for 15-30 min; and then washing the wool fibers with absolute ethanol at 40° C. for 5-15 min, rinsing the wool fibers with deionized water several times, and drying the washed wool fibers at 40-60° C.

In an implementation of the disclosure, the pretreatment may be carried out by using low-temperature plasma, and the formula and conditions of the treatment process are as follows: putting the wool fibers on a shelf in a low-temperature plasma treatment machine, turning on a vacuum pump, feeding oxygen, and clicking an automatic mode to carry out low-temperature plasma treatment on the wool fibers at a power of 100-150 W for 5-10 min.

In an implementation of the disclosure, the method for biologically enzymatical dyeing and improving the strength of wool fibers includes: sequentially adding the biocatalyst laccase and the phenolic compound to the buffer solution to prepare a reaction system with a pH of 4.0-6.0, and adding the pretreated wool fibers to the reaction system for reaction at 30-80° C. for 2-10 h.

In an implementation of the disclosure, the buffer solution is an acetic acid-sodium acetate buffer.

In an implementation of the disclosure, the concentration of the acetic acid-sodium acetate buffer solution is 0.1-0.3 mol/L.

In an implementation of the disclosure, the process formula and conditions for biologically enzymatical dyeing and improving the strength of wool fibers are as follows: preparing an acetic acid-sodium acetate buffer solution with a pH of 4.0-6.0, adding the catalyst laccase and the substrate to the buffer solution sequentially to make the laccase concentration 25-125 U/mL and the phenolic compound concentration 0.04-0.20 mol/L, adding the pretreated wool fibers to the reaction system at a bath ratio of 1:20 to 1:50, and raising the temperature to 30-80° C. for thermostatic reaction for 2-10 h.

In an implementation of the disclosure, the amount of the laccase used is (25-125) U/(0.04-0.20) mmol phenolic compound.

The second objective of the disclosure is to provide protein fibers prepared by the above method.

In an implementation of the disclosure, the protein fibers are wool.

The third objective of the disclosure is to provide yarn, thread and fabric containing the above wool.

Beneficial Effects

The disclosure uses the biocatalyst-laccase to catalyze the oxidation of a phenolic compound to produce a colored polymerization product. Protein fiber macromolecules contain a large number of active groups such as hydroxyl groups, amino groups and carboxyl groups, which easily react with colored enzymatic phenolic polymerization products to form covalent bonding, thereby realizing the dyeing of wool fibers and endowing wool good dyeing performance. The dyed wool shows a significantly improved tensile strength, an improved alkali resistance and oxidation resistance. The reaction conditions are mild, easy to control and environmentally friendly, and the method has favorable development prospects.

BRIEF DESCRIPTION OF FIGURES

FIGS. 1A to 1 c are SEM images of unmodified wool yarn and modified wool yarn in Examples 1 and 2, and the scales are 10 μm, wherein FIG. 1A shows a blank control group, FIG. 1B shows Example 1, and FIG. 1c shows Example 2.

FIGS. 2A to 2C are cross-section views (magnified 1000 times) of the unmodified wool yarn and the modified wool yarn in Examples 1 and 2, wherein FIG. 2A shows the blank control group, FIG. 2B shows Example 1, and FIG. 2C shows Example 2.

FIGS. 3A to 3C are pictures of the unmodified wool yarn and the modified wool yarn in Examples 1 and 2 after dyeing, wherein FIG. 3A shows the blank control group, FIG. 3B shows Example 1, and FIG. 3C shows Example 2.

FIG. 4 is a schematic diagram of a biologically enzymatical dyeing process.

DETAILED DESCRIPTION

The preferred examples of the disclosure will be described below. It should be understood that the examples are for better explaining the disclosure and are not intended to limit the disclosure.

Tensile strength test: The test is carried out on a tensile testing machine several times with a holding length of 180 mm and a tensile speed of 100 mm/min to take the average value. Determination of alkali solubility: The solubility of yarn is calculated with the weight of the yarn after alkali treatment and a solubility formula, to test the alkali damage resistance of the yarn. Determination of oxidation resistance: The oxidation resistance of yarn is determined by an ABTS method. The K/S value of wool yarn is tested with a colorimeter.

Example 1

(1) Pretreatment:

The formula and conditions of the treatment process were as follows: Sodium carbonate was dissolved in deionized water to prepare a sodium carbonate solution of 1 g/L. 1 g of wool yarn was weighed, and at a bath ratio of 1:30, the wool fibers were soaked in the sodium carbonate solution at 40° C. and treated for 15 min. Then the wool fibers were washed with absolute ethanol at 40° C. for 10 min and rinsed with deionized water, and the washed wool fibers were dried at 40° C.

(2) Enzyme-Catalyzed Reaction of a Phenolic Compound with Wool:

Preparation of a solution: An acetic acid-sodium acetate buffer of 0.2 mol/L was prepared and adjusted to a pH of 5.0. Catechol of 0.04 mol/L and laccase of 75 U/mL were added sequentially at a bath ratio of 1:30, and the mixed buffer was placed in the reactor to shake evenly. The pretreated wool yarn was put into the prepared buffer and reacted under shaking at a constant temperature of 40° C. for 5 h.

(3) After-Treatment:

After the wool yarn obtained in step (3) was taken out, enzyme deactivation was carried out by freezing at −50° C. for 12 h, and the wool yarn was washed with deionized water and dried naturally.

Example 2

(1) Pretreatment:

The formula and conditions of the treatment process were as follows: 1 g of wool yarn was put in a low-temperature plasma treatment machine, a vacuum pump was turned on, oxygen was fed, and an automatic mode was clicked to carry out low-temperature plasma treatment on protein fibers at a power of 100 W for 5 min.

(2) Enzyme-Catalyzed Reaction of a Phenolic Compound with Wool:

Preparation of a solution: An acetic acid-sodium acetate buffer of 0.2 mol/L was prepared and adjusted to a pH of 5.5. Catechol of 0.04 mol/L and laccase of 75 U/mL were added sequentially at a bath ratio of 1:50, and the mixed buffer was placed in the reactor to shake evenly. The pretreated wool yarn was put into the prepared buffer and reacted under shaking at a constant temperature of 40° C. for 5 h.

(3) After-Treatment:

After the wool yarn obtained in step (3) was taken out, enzyme deactivation was carried out by freezing at −40° C. for 12 h, and the wool yarn was washed with deionized water and dried naturally.

The properties of the wool obtained in Examples 1 and 2 were tested, and the results were shown in Table 1 and Table 2.

TABLE 1 Test results of the properties of wool fibers obtained in Examples 1 and 2 Oxida- Breaking Growth Breaking Alkali tion Different strength rate elongation solubility resistance treatment (cN) (%) (%) (%) (%) Raw wool 238.36 ± 6 — 29.74 ± 11 13.53 0.00 Example 1 272.01 ± 4 14.12 29.80 ± 10 9.69 64.50 Example 2 301.60 ± 7 26.53 34.00 ± 15 9.45 64.33

TABLE 2 Dyeing parameters of wool fibers obtained by different treatment methods in Examples 1 and 2 Indexes K/S L* a* b* Raw wool 0.24 91.56 −0.09 8.86 Example 1 18.33 21.78 4.56 4.90 Example 2 17.73 23.98 6.26 7.52

From the data in the tables, enzymatic polymerization dyeing of the wool yarn after different pretreatments could obtain favorable dye depths, and the wool yarn had improved strength to varying degrees, reduced alkali solubility, and improved oxidation resistance. More obviously, the enzymatically dyed wool yarn after the plasma pretreatment was increased by 26% in strength, and was better than the enzymatic polymerization dyed wool yarn chemically pretreated in mechanical properties.

Example 3 Investigating the Effect of Different Amounts of Laccase Used on Wool Fiber Dyeing

Referring to Example 1, the amounts of laccase used in step (2) were replaced by 25 U/mL, 50 U/mL, 100 U/mL and 125 U/mL respectively, and other conditions remained unchanged:

(1) Pretreatment:

The formula and conditions of the treatment process were as follows: 1 g of wool yarn and sodium carbonate were weighed, and the sodium carbonate was dissolved in deionized water to prepare a sodium carbonate solution of 1 g/L at a bath ratio of 1:30. The wool fibers were soaked in the sodium carbonate solution at 40° C. and treated for 15 min. Then the wool fibers were washed with absolute ethanol at 40° C. for 10 min and rinsed with deionized water, and the washed wool fibers were dried at 40° C.

(2) Enzyme-Catalyzed Reaction of a Phenolic Compound with Wool:

Preparation of a solution: An acetic acid-sodium acetate buffer of 0.2 mol/L was prepared and adjusted to a pH of 5.0. Catechol of 0.04 mol/L and laccase of 25 U/mL, 50 U/mL, 75 U/mL, 100 U/mL and 125 U/mL were added sequentially at a bath ratio of 1:30, and the mixed buffers were placed in the reactor to shake evenly. The pretreated wool yarn was put into the prepared buffers and reacted under shaking at a constant temperature of 40° C. for 5 h.

(3) After-Treatment:

After the wool yarn obtained in step (3) was taken out, enzyme deactivation was carried out by freezing at −50° C. for 12 h, and the wool yarn was washed with deionized water and dried naturally.

The properties of the obtained wool were tested, and the results were shown in Tables 3 and 4.

TABLE 3 Results of wool fibers dyed at different enzyme concentrations Amount of Oxida- laccase Breaking Growth Breaking Alkali tion used strength rate elongation solubility resistance (U/mL) (cN) (%) (%) (%) (%) Raw wool 238.36 ± 6 — 29.74 ± 11 13.53 0.00 10 240.21 ± 7 0.78 28.63 ± 10 13.23 10.35 25 261.57 ± 8 9.73 29.73 ± 12 11.30 51.73 50 270.75 ± 6 13.59 30.52 ± 10 10.05 57.49 75 272.01 ± 4 14.12 29.80 ± 10 9.69 64.50 (Exam- ple 1) 100 270.28 ± 9 13.39 24.04 ± 11 9.61 62.18 125 267.84 ± 7 12.37 24.43 ± 10 9.27 65.06 150 241.57 ± 6 1.35 20.64 ± 12 13.44 51.85

TABLE 4 Dyeing parameters of wool fibers obtained at different enzyme concentrations Amount of laccase used (U/mL) K/S L* a* b* Raw wool 0.24 91.56 −0.09 8.86 10 5.37 89.65 −0.02 9.76 25 12.03 43.52 7.89 8.82 50 15.64 31.33 6.97 7.88 75 18.33 21.78 4.56 4.90 (Example 1) 100 18.52 20.61 8.56 8.24 125 18.79 19.14 8.86 8.87 150 20.76 39.31 8.54 10.35

From the data in the tables, when the enzyme concentration was low, the yarn had high dye depth and breaking strength, a gradually decreasing L* value (decreasing lightness), positive a* and b* values, and a dark brown color. With the increase of the enzyme concentration, the yarn had decreasing alkali solubility, slightly increasing oxidation resistance, but still unfavorable effect. When the enzyme concentration exceeded 75 U/mL, the breaking strength and dye depth tended to be stable. When the laccase concentration was too high (150 U/mL), the dye depth slightly increased, but the strength improving effect decreased, causing waste of the reagent and diseconomy.

Example 4 Investigating the Effect of Different Catechol Concentrations on Wool Fiber Dyeing

Referring to Example 1, the reaction concentrations of phenolic substrates used in step (2) were replaced by 0.08 mol/L, 0.12 mol/L, 0.16 mol/L and 0.20 mol/L respectively, and other conditions remained unchanged:

(1) Pretreatment:

The formula and conditions of the treatment process were as follows: 1 g of wool yarn and sodium carbonate were weighed, and the sodium carbonate was dissolved in deionized water to prepare a sodium carbonate solution of 1 g/L at a bath ratio of 1:30. The wool fibers were soaked in the sodium carbonate solution at 40° C. and treated for 15 min. Then the wool fibers were washed with absolute ethanol at 40° C. for 10 min and rinsed with deionized water, and the washed wool fibers were dried at 40° C.

(2) Enzyme-Catalyzed Reaction of a Phenolic Compound with Wool:

Preparation of a solution: An acetic acid-sodium acetate buffer of 0.2 mol/L was prepared and adjusted to a pH of 5.0. Catechol of 0.08 mol/L, 0.12 mol/L, 0.16 mol/L and 0.20 mol/L and laccase of 75 U/mL were added sequentially at a bath ratio of 1:30, and the mixed buffers were placed in the reactor to shake evenly. The pretreated wool yarn was put into the prepared buffers and reacted under shaking at a constant temperature of 40° C. for 5 h.

(3) After-Treatment:

After the wool yarn obtained in step (3) was taken out, enzyme deactivation was carried out by freezing at −50° C. for 12 h, and the wool yarn was washed with deionized water and dried naturally.

The properties of the obtained wool were tested, and the results were shown in Tables 5 and 6.

TABLE 5 Results of wool fibers dyed at different catechol concentrations Catechol Oxida- concen- Breaking Growth Breaking Alkali tion tration strength rate elongation solubility resistance (mol/L) (cN) (%) (%) (%) (%) Raw wool 238.36 ± 6 — 29.74 ± 11 13.53 0.00 0.02 230.51 ± 5 −3.29 24.79 ± 9  12.51 40.37 0.04 272.01 ± 4 14.12 29.80 ± 10 9.69 64.50 (Exam- ple 1) 0.08 268.25 ± 7 12.54 23.69 ± 10 9.07 67.71 0.12 257.60 ± 6 8.07 17.80 ± 12 8.92 69.16 0.16 256.01 ± 8 7.40 15.48 ± 11 9.38 70.97 0.4  225.58 ± 7 −5.36 12.65 ± 13 10.34 80.63

TABLE 6 Dyeing parameters of wool fibers obtained at different catechol concentrations Catechol concentration (mol/L) K/S L* a* b* Raw wool 0.24 91.56 −0.09 8.86 0.02 3.68 80.52 2.37 9.76 0.04 18.33 21.78 4.56 4.90 (Example 1) 0.08 19.08 20.35 3.46 6.57 0.12 20.15 18.27 6.14 12.32 0.16 20.49 14.84 4.56 17.29 0.4  30.24 1.36 8.67 7.96

From the data in the tables, it can be seen that under the catalysis of the laccase, with the increase of the catechol monomer concentration, the wool yarn had gradually increasing dye depth, a dark brown color, and improved alkali resistance and oxidation resistance. However, with the increase of the amount of phenol used, the breaking strength of the yarn first increased and then decreased, and the breaking elongation decreased with the increase of the amount of phenol used. When the substrate concentration was low (e.g. 0.02 mol/L), the dyeing and strength were not significantly improved. When the substrate concentration was too high (e.g. 0.4 mol/L), the dye depth increased, but the dyeing was uneven, the yarn strength decreased, the breaking elongation decreased, the hand feeling was hard and the elasticity decreased.

Example 5 Investigating the Effect of Different Reaction Temperatures on Wool Fiber Dyeing

Referring to Example 1, the reaction temperatures in step (2) were replaced by 30° C., 50° C., 60° C., 70° C. and 80° C. respectively, and other conditions remained unchanged:

(1) Pretreatment:

The formula and conditions of the treatment process were as follows: 1 g of wool yarn and sodium carbonate were weighed, and the sodium carbonate was dissolved in deionized water to prepare a sodium carbonate solution of 1 g/L at a bath ratio of 1:30. The wool fibers were soaked in the sodium carbonate solution at 40° C. and treated for 15 min. Then the wool fibers were washed with absolute ethanol at 40° C. for 10 min and rinsed with deionized water, and the washed wool fibers were dried at 40° C.

(2) Enzyme-Catalyzed Reaction of a Phenolic Compound with Wool:

Preparation of a solution: An acetic acid-sodium acetate buffer of 0.2 mol/L was prepared and adjusted to a pH of 5.0. Catechol of 0.04 mol/L and laccase of 75 U/mL were added sequentially at a bath ratio of 1:30, and the mixed buffer was placed in the reactor to shake evenly. The pretreated wool yarn was put into the prepared buffer and reacted under shaking at different constant temperatures for 5 h.

(3) After-Treatment:

After the wool yarn obtained in step (3) was taken out, enzyme deactivation was carried out by freezing at −50° C. for 12 h, and the wool yarn was washed with deionized water and dried naturally.

The properties of the obtained wool were tested, and the results were shown in Tables 7 and 8.

TABLE 7 Results of wool fibers dyed at different temperatures Temper- Breaking Growth Breaking Alkali Oxidation ature strength rate elongation solubility resistance (° C.) (cN) (%) (%) (%) (%) 30 255.59 ± 6 7.23 21.08 ± 6 10.34 53.79 40 272.01 ± 4 14.12  29.80 ± 10 9.69 64.50 (Exam- ple 1) 50 267.69 ± 8 12.3 26.87 ± 6 11.30 62.33 60 252.08 ± 6 5.76  22.26 ± 10 10.05 60.75 70 240.98 ± 9 1.10 24.62 ± 9 9.61 62.36 80 218.15 ± 7 −8.48 19.91 ± 8 9.27 58.64

TABLE 8 Dyeing parameters of wool fibers obtained at different temperatures Temperature (° C.) K/S L* a* b* 30 12.01 41.56 3.09 6.86 40 18.33 21.78 4.56 4.90 (Example 1) 50 19.63 34.33 7.97 7.58 60 18.33 20.78 4.46 4.93 70 16.64 21.27 6.04 12.37 80 15.02 20.81 8.76 9.24

From the data in the tables, when the temperature was lower than 50° C., the dye depth and breaking strength of the dyed yarn increased with the increase of temperature; and when the temperature was higher than 50° C., the breaking strength and dye depth of the wool yarn decreased slowly with the increase of temperature.

Although the disclosure has been disclosed as above in the preferred examples, it is not intended to limit the disclosure. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the disclosure. The protection scope of the disclosure should be as defined in the claims. 

What is claimed is:
 1. A method for improving the strength of wool fibers, comprising: adding laccase and a phenolic compound to a buffer solution to form a mixed system; and then, putting wool fibers in the obtained mixed system to react at a constant temperature of 30-80° C.; wherein the laccase concentration in the mixed system is 25-125 U/mL; and the concentration of the phenolic compound is 0.04-0.20 mol/L.
 2. The method according to claim 1, wherein the phenolic compound is one or more of catechol, hydroquinone, gallic acid, vanillin and guaiacol.
 3. The method according to claim 1, wherein the buffer solution is an acetic acid-sodium acetate buffer.
 4. The method according to claim 3, wherein the acetic acid-sodium acetate buffer solution has a concentration of 0.1-0.3 mol/L, and a pH of 4.0-6.0.
 5. The method according to claim 1, wherein at a bath ratio of 1:20 to 1:50, the wool fibers are added to the mixed system.
 6. The method according to claim 1, wherein the reaction is carried out at a constant temperature of 30-80° C. for 2-10 h.
 7. Wool fibers, having the fiber strength improved by the method according to claim
 1. 8. Yarn, thread or fabric containing the wool fibers according to claim
 7. 